As seen from the Arctic, the Sun is above the horizon for 24 continuous hours at least once per year (and therefore visible at midnight) and below the horizon for 24 continuous hours at least once per year (and therefore not visible at noon). This is also true in the Antarctic region, south of the equivalent Antarctic Circle.

The position of the Arctic Circle is not fixed; as of 15 September 2019, it runs 66°33?47.8? north of the Equator.[3] Its latitude depends on the Earth's axial tilt, which fluctuates within a margin of more than 2° over a 41,000-year period, due to tidal forces resulting from the orbit of the Moon.[4] Consequently, the Arctic Circle is currently drifting northwards at a speed of about 15 m (49 ft) per year.

Etymology

The word arctic comes from the Greek word (arktikos: "near the Bear, northern")[5] and that from the word (arktos: "bear").[6]

Midnight sun and polar night

Relationship of Earth's axial tilt (?) to the tropical and polar circles

Directly on the Arctic Circle these events occur, in principle, exactly once per year: at the June and Decembersolstices, respectively. However, because of atmospheric refraction and mirages, and also because the sun appears as a disk and not a point, part of the midnight sun may be seen on the night of the northern summer solstice up to about 50 minutes (?) (90 km (56 mi)) south of the Arctic Circle; similarly, on the day of the northern winter solstice, part of the sun may be seen up to about 50? north of the Arctic Circle. That is true at sea level; those limits increase with elevation above sea level, although in mountainous regions there is often no direct view of the true horizon.

Human habitation

Cylindrical projection showing the Arctic Circle in red

Only four million people live north of the Arctic Circle due to the climate; nonetheless, some areas have been settled for thousands of years by indigenous peoples, who today make up 10% of the region's population.[8] Tens of thousands of years ago, waves of people migrated from eastern Siberia across the Bering Strait into North America to settle.

The largest communities north of the Arctic Circle are situated in Russia, Norway, and Sweden: Murmansk (population 295,374), Norilsk (178,018), Tromsø (75,638), Vorkuta (58,133), and Kiruna (16,936). Rovaniemi (62,667) in Finland is the largest settlement in the immediate vicinity of the Arctic Circle, lying 6 km (4 mi) south of the line.

In contrast, the largest North American community north of the Arctic Circle, Sisimiut (Greenland), has approximately 5,000 inhabitants. Of the Arctic communities in Canada and the United States, Utqiagvik, Alaska is the largest settlement with about 4,000 inhabitants.

Climate

The climate inside the Arctic Circle is generally cold, but the coastal areas of Norway have a generally mild climate as a result of the Gulf Stream, which makes the ports of northern Norway and northwest Russia ice-free all year long. In the interior, summers can be quite warm, while winters are extremely cold. For example, summer temperatures in Norilsk, Russia will sometimes reach as high as 30 °C (86 °F), while the winter temperatures frequently fall below -50 °C (-58 °F).

Sites along the Arctic Circle

Starting at the prime meridian and heading eastwards, the Arctic Circle passes through: